THE MARSUPIALS, OR POUCHED ANIMALS. 95 



deciduous tooth, is not a safe starting point for 

 making a satisfactory comparison of their denti- 

 tion with that of the Eutheria (the higher Mam- 

 mals). 



In an interesting paper on the classification of 

 the Mammalia, Huxley l says : ' As Professor 

 Flowers has pointed out, the question arises 

 whether we have here a primary dentition with 

 only one secondary tooth, or a secondary dentition 

 with only one tooth of the primary set left. I 

 have no doubt that the answer given to this ques- 

 tion by Prof. Flowers is correct, and that it is 

 the milk dentition of which only a vestige is left 

 in Marsupialia. Among existing Eodents, in fact, 

 all conditions of the milk dentition exist from a 

 number equal to that of the permanent incisors and 

 premolars (as in the rabbit) to none at all. The 

 same thing is observed in the Insectivora, where 

 the Hedgehog, and probably Centetes, have a full 

 set of milk teeth while none have yet been found 

 in the Shrews. In these cases it is obvious that the 

 milk dentition has gradually been suppressed in 

 the more modified forms ; and I think that there 



1 ' On the Application of the Laws of Evolution to the Arrange- 

 ment of the Vertebrata, and more particularly of the Mammalia ' 

 (Kosmos, ix. 1881). 



